TOO GOOD TO BE TRUE?!?!

So I am on my 5th and final pregnancy ladies. This time around it is KILLING me to know gender! More than any pregnancy even my first!! I literally stay on Google all hours of the day! I've done every theory test imaginable (some several). Anyway with all my previous pregnancies I found out at 16 weeks. (Same Dr) This time around I have a new OB and they absolutely won't look until 20 weeks ( next sono). I was on Google and found a place about 2 he's from me that will do gender ultrasounds at 13 weeks!!!! For 75$!!!! And they say 100% guaranteed but say they've never been wrong!! I'm so skeptical!! I've read all the reviews and they only have like 2 or 3 negative ones and only one person saying that they were wrong about her gender. She said that 20 week sono showed different gender but they commented and asked her to come back and update when the kid is born which she hasn't done! Is it too good to be true ladies!!???!!!! I made the appointment but now I'm a little weary at wasting 75 dollars and gas and a drive but even more than that I don't wanna get my hopes up for wrong gender and buy a bunch of stuff.... Any advice???